Progress in nickel oxide semiconductors for quantum dot-based electroluminescent devices

Abstract

The efficiency of quantum-dot light-emitting diodes (QLEDs) has improved, with the efficiency of red, green, and blue QLED devices exceeding 20%. However, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) materials commonly used in QLEDs suffer from several drawbacks, such as hygroscopicity and a tendency to corrode ITO electrodes, which negatively affect the device operation time and commercial viability. As p-type oxide semiconductors, NiO_x exhibits high optical transparency, a tunable work function and an adjustable electronic structure, which enable it to be suitable for use as a hole injection layer (HIL) with electron-blocking properties. Furthermore, low-cost fabrication is required to form a charge transport layer at low temperatures by a solution process. In this review, different solution methods for preparing NiO_x and the recent advances in the development of NiO_x based QLEDs are both summarized. More stable QLEDs are obtained through NiO_x modification, doping, post-treatment, device structural optimization, and so on. The potential future research directions are outlined to guide further advancements in QLED technology and further studies to fully understand it at a deeper level are highly needed.